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LM5010: Driving a Capacitive Load

Intellectual 260 points

Replies: 8

Views: 148

Part Number: LM5010

Hello,

I am considering using the lm5010 to top off the voltage on a 470uF capacitor bank which will provide a 10A 150us pulse to another application. 

I got the AN-1352 LM5010 Evaluation Board and changed R3 to 22k in order for it to put out 52.5V, changed R1 to 470k to change the switching frequency to 920kHz and attached the 470uF load on vout. (Vin is set to 60V).

However, as soon as i attached the load, the output voltage dropped as the chip attempted to charge the capacitor. It would rise to 51.6v and then abruptly stop switching. The voltage would continue to fall until 1.2v until the lm5010 would start switching again.

Any clue how I could get the chip to stay switching?

Best,

-Danny

8 Replies

  • P.S

    The blue is the voltage at SW pin and yellow is at Vout

  • In reply to Danny Andreev:

    Hi Danny,

    Please share your schematic design.Did you also change R2 in your feedback network, because I don't think the R3 change is enough for a 52.5 V output.

    Regards,

    Ethan

  • In reply to Ethan T:

    I left R2 as 1k and R3 as 20k (mistyped 22k)

    Vout=2.5*(r1+r2)/r2

    Vout=2.5*(20k+1k)/1k=52.5V

  • In reply to Danny Andreev:

    Hi Danny,

    Is your schematic the same as the EVM with changed feedback resistors? Did you leave C7 and added the capacitive load? I suggest increasing the SS capacitor in case the device is ramping too fast and possibly hitting current limit.

    Regards,

    Ethan

  • In reply to Ethan T:

    I switched to the LM5118 for other reasons, Not sure what was wrong in this circuit

  • In reply to Danny Andreev:

    Hi Danny,

    Understood. Are you seeing the same problem with the LM5118 or has all your issues been resolved?

    Regards,

    Ethan

  • In reply to Ethan T:

    I am having other issues with the lm5118 which I am discussing in this thread:

    https://e2e.ti.com/support/power-management/f/196/t/847987

  • In reply to Danny Andreev:

    Hi Danny,

    Understood. I hope your issue gets resolved.

    Regards,

    Ethan

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